The use of sulfur mustard, bis-(2-chloroethyl) sulfide (HD) in chemical warfare has been long known. More recently its use in the Iran-Iraq conflict resulted in many deaths and untold suffering. It's use was a major threat in the Gulf War. Hence, the method of identifying injury due to mustards is an important pursuit for scientists working for the armed forces.
It is believed that nitrogen and sulfur mustard-induced vesication wherein there is separation of the epidermis from the dermis due to the disruption of the connective tissues may be the result of a specific protease. The exact mechanism of its toxicity remains unclear and no effective antidote has yet been reported in the literature. DNA is considered to be its major intracellular target (Papirmeister et al., 1985). Other toxic effects are protease stimulation, cutaneous degradation and blister formation. Smith et al. (1991) and Cowan et al. (1991 ) have demonstrated that HD and another vesicating agent chloroethylethyl sulfide (CEES) stimulate protease activity in NHEK, Hela Cell line and in human peripheral blood lymphocytes. No information, however, exists with respect to the molecular mechanism of mustard-induced protease activation.
Immunohistochemical studies have been done on the protein composition changes in HD-exposed hairless guinea pig skin. Epidermal-dermal junction proteins, namely, bullous pemphigoid antigen, laminin and hemidesmosomal anchoring filament proteins were affected by exposure to HD. More recently, investigators have found that in the mini pig skin, which is more akin to human skin, only one protein in the lamina lucida, thelamini, is affected by HD. These findings strongly suggest that some specific protease(s) may be responsible for HD-induced vesication.
The concept that a specific protease is involved in pathology related to exposure to mustards is important because the use of generalized protease inhibitors could cause serious side-effects. Cowman, et al. have demonstrated that HD and chloroethyl ethyl sulfide (CEES) stimulate protease activity in vitro in human peripheral blood lymphocytes and in vivo in hairless guinea pig skin. However, a definitive characterization of the mustard-stimulated protease is not described in any previous publication.